Who is godd at physics An astronaut travels at 0.93c. As one hour passes for her
ID: 2108170 • Letter: W
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Who is godd at physics
An astronaut travels at 0.93c. As one hour passes for her how much time passes for an observer on earth? A spaceship passes you at 0.9c. You note its length to be 80.0 m. How long is it when at rest? At what speed will an object's mass be twice its rest mass? Ideally, how much energy could be obtained from a 500 g golf ball? How long could that energy run a 150 W light bulb (remember, P=E/t)? Two dragsters approach each other in a game of "chicken" at 80 mph, what is the speed of each with respect to the other? Two space dragsters play a similar game at much higher speeds, they approach each other at speeds of 0.6c. What speed is each going with respect to the other? The nearest star, Proxima Centauri, is 4.3 light years away. How fast would you have to go to make the trip seem like a distance of 1000 km? One light year is approximately equal to 9.5 x 10l2km. A farm boy studying physics believes he can get a 12-m-long pole into a 10-m-long bam if he runs fast enough (carrying the pole of course). Can he do it? Explain. How does your answer deal with the fact that when he is running the bam looks even shorter to him?Explanation / Answer
Number 1
Apply t = t'/(1 - v^2/c^2)^.5
t = 1/(1 - .93^2)^.5
t = 2.72 hours
Number 2)
L = L'(1 - v^2/c^2)^.5
80 = L'(1 - .9^2)^.5
L' = 183.5 m
Number 3)
mo/(1 - v^2/c^2)^.5 = 2mo
1/4 = (1 - v^2/c^2)
v = 2.60 X 10^8 m/s which is .866c
Number 4)
E = mc^2
E = (.5)(3 X 10^8)^2 = 4.5 x 10^16 Joules
P = E/t
t = E/P = 4.5 X 10^16/150 = 3 X 10^14 seconds
That is 8.33 X 10^10 hours or 3.47 X 10^9 days, or even 9.51 X 10^6 years
Number 5)
For the normal speeds, each seems to travels at 160 mph to the other
In relativistic terms apply relativistic velocity addition
u' = u-v/(1 - uv/c^2)
u' = (.6 -(-.6))/(1 -.6(-.6))
u' = .882c
Number 6)
L = L'(1 - v^2/c^2)^.5
1000 = (4.3)(9.5 X 10^12)(1 - v^2/c^2)^.5
5.993 X 10^-22 = 1-v^2/c^2
v = 2.99999999.99 X 10^8 m/s which is .99999999998776 c
Number 7)
No, he can not do it. His logic is all wrong. The pole is at rest to him, so it will always remain 12 ft long. The barn will actually appear shorter, so he would actually have less room to make the pole fit. Overall, his thinking is backwards.
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